HOLOCENE EVOLUTION OF THE CHANGUINOLA PEAT DEPOSIT, PANAMA: SEDIMENTOLOGY OF A MARINE-INFLUENCED TROPICAL PEAT DEPOSIT ON A TECTONICALLY ACTIVE COAST by Stephen Phillips B .A., University of Waterloo, 1971 B.Sc., University of Victoria, 1990 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF GEOLOGICAL SCIENCES We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March, 1995 © Stephen Phillips, 1995 _____________________ In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. (Signature) Department of (E&-çfc4-L The University of British Columbia Vancouver, Canada Date /3///9s_: ABSTRACT The evolution and structure of a large peat deposit on the Caribbean coast of western Panama, Central America is evaluated as a possible analogue for the deposition of low-ash, low sulphur coals. Effects of earthquake-driven subsidence events on the peat and the peat-forming vegetation are investigated, and implications of tectomc subsidence on the evolution of this deposit and on the currently developing model of coastal tropical coal deposition are described. The deposit is approximately 80 km2 in extent, averages 6.5 m in thickness, and occupies the width of the narrow coastal plain between the Talamanca Cordillera and barrier beach on a seismically active part of the Caribbean coast. Based on vegetation zonation , topography and hydrology, the modern Changuinola mire complex can be divided into a raised, concentrically zoned, ombrotrophic western section, and a dissected and partially rheotrophic eastern section. Differing hydrological regimes of these two sections are reflected in the physical and chemical stratigraphy of the peat. In the western section, a vertical succession of peat types, highly humified at the base and margins, and more fibric in the upper central part, is the result of internal hydrological boundaries, created by density and permeability variations in the peat. The mire is insulated from marine and fluvial influences by topography and hydrology, and displays no evidence of fluctuating sea level. Coal formed in such an environment would be low in sulphur and ash, dull and massive at the base and margins, and finely banded in the upper central part. The eastern section of the mire is in part rheotrophic, with a complex mosaic of vegetation types, and is segmented into distinct drainage areas by tidal blackwater creek channels. Effects of this marine influence are localized to the bay and channel margins. Coals formed 11 in this environment would have large variations in sulphur over distances of a few metres laterally, and a few centimetres vertically. Earthquake-driven coastal subsidence is greatest in the southeast, and has lead to drowning of the deposit. Subsidence events raise the level in the blackwater creeks, moving the front of marine influence to the northwest (inland), and leading to the replacement of freshwater vegetation with mangroves. The degree of penetration of marine waters remains restricted, however, to marginal peats. An increase in the scale of subsidence events may overcome the response capability of the mangroves and lead to disruption of internal hydrological boundaries and ultimate deflation and drowning of the mire. 111 TABLE OF CONTENTS ABSTRACT ii TABLE OF CONTENTS iv LIST OF FIGURES LIST OF PLATES xi LIST OF TABLES xii DEDICATION xiii ACKNOWLEDGEMENTS xiv FOREWORD xv CHAPTER 1: iNTRODUCTION 1 1.1 OBJECTiVES 2 1.2 PRESENTATION 6 1.3 REFERENCES CITED 8 CHAPTER 2: SEDIMENTOLOGY OF THE CHANGUINOLA PEAT DEPOSIT: 9 ORGANIC AND CLASTIC SEDIMENTARY RESPONSE TO PUNCTUATED COASTAL SUBSIDENCE 2.1 ABSTRACT 10 2.2 INTRODUCTION 12 2.3 METHODS 14 a) Measures ofEarthquake-induced Subsidence 14 b) Levelling Surveys 17 c) Remote Sensing 17 d) Hydrology 19 e) Clastic Sediments 19 J) Vegetation Survey 19 g) Peat Sampling 21 h) Peat Characterization 21 2.4 GEOLOGICAL SETTING 26 2.5 GEOMORPHOLOGY 28 2.6 VEGETATION 30 2.7 AGE AND GEOMETRY OF THE DEPOSIT 31 iv 2.8 SEA LEVEL CHANGE AND PUNCTUATED SUBSIDENCE 34 a) Subsidence in 1991 35 b) Long Term Sea Level Change 38 2.9 ORGANIC M”D) CLASTIC SEDIMENTOLOGY 40 2.9.1 CLASTIC SEDIMENTS 40 a) Changuinola River Floodplain 40 b) Barrier System 43 i) Sedimentary Structures 43 ii) Grain Size andMineralogy 43 c) Peat Basal Sediments 45 d) Almirante Bay 45 2.9.2 ORGANIC SEDIMENTATION 48 a) Peat Characterization 48 b) Geochemical Parameters 50 c) Degree ofHum/Ication, Ash and Moisture Content 51 i) Western Section 54 ii) Eastern Section 56 2.10 DISCUSSION 59 2.10.1 CLASTIC SEDIMENTARY RESPONSE TO RECENT TECTONISM 59 a) Changuinola River Floodplain 59 b) Barrier Beach 61 2.10.2 HYDROLOGICAL CONTROLS ON PEAT ACCUMULATION 62 a) Western Section 63 b) Eastern Section 67 2.10.3 IMPLICATIONS FOR COAL GEOLOGY 71 a) Transgressive and Regressive Signatures and the Relation ofPeat Deposition to 71 Active Clastic Sedimentation 2.11 CONCLUSIONS 74 2.12 REFERENCES CITED 77 CHAPTER 3: VEGETATION ZONES AND DIAGNOSTIC POLLEN PROFILES OF A 82 COASTAL PEAT SWAMP, BOCAS DEL TORO, PANAMA 3.1 ABSTRACT 83 3.2 iNTRODUCTION 85 3.3 GEOGRAPHY AND CLIMATE 88 3.4 METHODS 90 a) Problems 90 b) Satellite Imagery 92 c) Levelling Surveys 92 d) Coring ofPeat and Collection ofSurface Samples 92 e) Collection and Identification ofPlants 95 fi Peat Classfication, Pollen Preparation and Identification 95 g) Pollen Counts and Pollen Diagrams 96 3.5 RESULTS AND INTERPRETATION 97 a) Vegetation Distribution 97 98 1) Mappable Vegetation Zones ii) Description ofthe Phasic Communities 99 3.6 POLLEN DISTRIBUTION 110 V a) Surface Pollen Diagrams 110 b) Pollen From Cores 116 3.7 DISCUSSION 121 3.8 SUMMARY AND CONCLUSIONS 126 3.9 REFERENCES CITED 129 CHAPTER 4: SULPHUR IN THE CHANGUINOLA PEAT DEPOSIT AS AN 133 INDICATOR OF THE ENVIRONMENTS OF DEPOSITION OF PEAT AND COAL 4.1 ABSTRACT 134 4.2 iNTRODUCTION 135 4.3 REGIONAL SETTING 137 a) Geography, Climate and Biology 137 b) Geomorphology 139 c) Geological Setting 140 4.4 SAMPLiNG AND EXPERIMENTAL 140 4.5 RESULTS 142 a) Geochemical Parameters 142 142 1) Sulphur and Salinuy ii) Sulphur andp1-I 145 b) Total Sulphur Distribution 148 I) Sulphur andpH in the Western Section of the Deposit 148 ii) Sulphur, Salinity andpH in the Eastern Section ofthe Deposit 152 c) Forms ofSulphur 154 154 1) B13: An Example ofa Group III Peat ii) BDD 23: An Example ofGroup land Group IlPeats 159 4.6 DISCUSSION 162 a) Sulphur, pH and Marine Influence 162 b) Sulphur and Vegetation 163 c) Sulphur and Climatic Influence 166 d) Sulphur and Tectonic Influence 167 4.7 IMPLICATIONS FOR ENVIRONMENTAL STUDIES OF COAL 168 4.8 CONCLUSIONS 170 4.9 REFERENCES CITED 172 176 CHAPTER 5: EARTHQUAKE-INDUCED FLOODING OF A TROPICAL COASTAL PEAT SWAMP: A MODERN ANALOGUE FOR HIGH SULPHUR COALS 5.1 ABSTRACT 177 5.2 INTRODUCTION 178 5.3 SAMPLING AND EXPERIMENTAL PROCEDURES 180 5.4 RESULTS 180 a) Total Sulphur, Salinity and p1-f 180 b) Forms ofSulphur 183 183 z) Organic Forms ii) Inorganic Forms 183 5.5 DISCUSSION 185 5.6 CONCLUSIONS 188 vi 5.7 REFERENCES CITED 190 CHAPTER 6: CONCLUSIONS 191 6.1 CONCLUSIONS 191 6.2 SUGGESTIONS FOR FURTHER RESEARCH 193 APPENDICES 195 APPENDIX A SAMPLE SITE LOCATIONS AND ANALYTICAL KEY 195 APPENDIX B SAMPLE DESCRIPTIONS 198 APPENDIX C RESULTS OF WET SIEViNG 216 APPENDIX D POLLEN COUNTS FROM CORES 222 APPENDIX E POLLEN DESCRIPTIONS AND PLATES 225 APPENDIX F RESULTS OF VEGETATION SURVEY 233 APPENDIX G ANALYTICAL PROCEDURES AND DEFiNITIONS 235 APPENDIX H REMOTE SENSING 243 APPENDIX I LEVELLING SURVEYS 244 vii LIST OF FIGURES Figure 1.1 Regional map of southern Central America showing major tectonic elements. 3 Figure 1.2 Landsat satellite image of western Panama and eastern Costa Rica. 4 Figure 2.1 Large map shows general geology of part of the Limon - Bocas del Toro Basin, 15 and bathymetry of the continental shelf off the study area in northwestern Panama. Insert shows the location of the study area. Figure 2.2 Areas of observed and modelled uplift and subsidence along the Caribbean coast 16 of Panama and Costa Rica as a result of the April 22, 1991 Ms=7.5 earthquake. Figure 2.3 Colour infrared air photo of part of the subsided margin of the peat deposit along 18 the shore of Almirañte Bay. Figure 2.4. Map of the study area showing sample sites referred to in the text. 20 Figure 2.5. Cross sections and high and low discharge rates in the three largest brackish 22 blackwater creeks. Figure 2.6. The western half of the barrier beach, and cross sections of the barrier at the 23 beach end of the surveyed transect. Figure 2.7. False colour SPOT satellite image of the area of the detail map marked in Figure 24 2.1, including the Changuinola peat deposit. Figure 2.8. False colour SPOT satellite image of the narrow coastal plain and barrier 24 shoreline. Figure 2.9. Upper panel. SW-NE cross section of the peat deposit along survey line. Lower 33 panel: Results of particle size analysis (wet sieving) of 8 cores across the western part of the deposit. Figure 2.10.